To accomplish long term (7-10 days) organ preservation necessary for optimum donor recipient matching a new approach is indicated. Previous work in this laboratory over the past 3 years has documented that hypothermia itself has direct harmful effects on tissues or nonhibernating animals. This damage is species and time dependent. The proposed research project will focus on the solution of two problems: 1) What is the lowest temperature range at which tissues of homeotherms, especially man, are able to maintain the functional and structural integrity? 2) How can perfusion be adequately performed at this temperature? The answer to the first problem will be studied by using cell cultures and incubated separated renal tubular fragments. After the optimum temperature has been established, organ (kidney) perfusion will be studied at that temperature with specific attention to the following parameters: 1) Optimum flow and pressure; 2) adequacy of intrarenal perfusate and oxygen distribution; 3) adequacy of oxygenation; 4) optimum substrate utilization and elimination of waste products; 5) maintenance of endothelial integrity; 6) maintenance of sterility; and 7) evaluation of adequacy of storage.